I noticed that loading MarkUs from localhost with Firefox was taking much much longer than it took with Chrome or even IE. I thought this was just due to my many development add-ons but when I looked at the page loading with firebug I noticed that most of the time was spent on DNS lookup. From searching online, it seems that this is a known issue that occurs because Firefox is trying to find an IPV6 address for localhost but only receiving an IPV4 address.
To make things faster, go to about:config and set network.dns.ipv4OnlyDomains to the value “localhost”. Now Firefox only tries to find an IPV4 address 🙂